The present invention relates to an oil pump unit for an outboard motor.
An engine unit of an outboard motor is mounted vertically in such a way that a crank shaft of an engine is vertically disposed. The engine is formed by assembling a crank case, a cylinder block, a cylinder head and the like. If the engine is a four-stroke-cycle engine, an oil pan is disposed below the engine. A lubricating device having an oil pump for pumping up oil accumulated in the oil pan is provided to lubricate the inside portion of the engine.
A conventional lubricating device for an outboard motor is disclosed in, for example, Japanese Patent Laid-Open Publication No. HEI 8-100614. The disclosed device has a structure that an oil pan is disposed below a cylinder block and a cylinder head. An oil pump is, in the oil pan, disposed below the cylinder head and is operated by a cam shaft rotatively supported in the cylinder head.
Another conventional lubricating apparatus for an outboard motor is disclosed in, for example, Japanese Patent Laid-Open Publication No. HEI 5-26175. The disclosed device has a structure that an oil pan is joined to a portion of the crank shaft which projects over the lower surface of the engine. The oil pump is directly operated by the crank shaft.
If the oil pump is joined to the lower surface of the engine, an operation for solely removing the engine unit from the outboard motor for maintenance or the like is performed in a state where the oil pump appears and projects over the lower portion of the engine. Thus, it is inconvenient because the engine cannot be placed on a flat workbench to perform the maintenance. Furthermore, there is apprehension that the engine may be damaged because of an external factor.
If a member, for example, a, crank shaft, except for the cam shaft is employed as a drive shaft for the oil pump, the disposed drive shaft obstructs an oil dropping passage formed from the crank case to the oil pan. Thus, there is apprehension that the oil dropping performance is deteriorated.